I'll give you a hint: It's not Call of Duty: Ghosts - Digital Hardened Edition.
Defy Gravity Extended has gone down in history as the cheapest game in Steam's "Summer Sale." The indie action title went on sale for a mere $0.29 (90 percent off) at the start of this years annual sale on June 19, 2014.
You'd expect Defy Gravity Extended to be mediocre title for $0.29... but that game scored a solid 8 (out of 10) score on IGN for its interesting, challenging and varied gameplay.
The next cheapest title in this years "Summer Sale" is Afterfall Insanity - Dirty Arena Edition with a $0.33 (67 percent off) price tag; but unlike Defy Gravity Extended, Afterfall Insanity - Dirty Arena Edition is digital s*it.